Inositol Phosphates: Inframolecular Physico-Chemical Studies: Correlation with Binding Properties

Schlewer, Gilbert; Guédat, Philippe; Ballereau, Stéphanie; Schmitt, Laurent; Spiess, Bernard

doi:10.1021/bk-1999-0718.ch017

Cited by 5 publications

(19 citation statements)

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“…For micellar PI-4,5-P 2 , the 4# position exhibited a pK a2 value of 6.7, whereas for the 5# position the pK a2 equaled 7.6 (van Paridon et al, 1986). Similar dependencies of the pKa 2 values were found for inositol phosphates (Schlewer et al, 1999). Although these pKa 2 variations are expected to modulate slightly the mutual phosphatidylinositol monophosphate interaction, it can be safely assumed that at high pH (pH 8-9) the phosphomonoester group is largely deprotonated for all PI-xP derivatives.…”

Section: Phosphatidylcholine/phosphatidylinositol Monophosphate Mixed Vesiclessupporting

confidence: 69%

Domain Formation in Phosphatidylinositol Monophosphate/Phosphatidylcholine Mixed Vesicles

Redfern

Gericke

2004

Biophysical Journal

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Phosphoinositides have been shown to control membrane trafficking events by targeting proteins to specific cellular sites, which requires a tight regulation of phosphoinositide generation and turnover as well as a high degree of compartmentalization. To shed light on the processes that lead to the formation of phosphoinositide-enriched microdomains, phosphatidylcholine/phosphatidylinositol monophosphate (phosphatidylinositol-3-phosphate (PI-3P), -4-phosphate (PI-4P), or -5-phosphate (PI-5P)) mixed vesicles were investigated by calorimetric (DSC) Fourier transform infrared spectroscopic (FTIR), and fluorescence resonance energy transfer (FRET) measurements. The experiments furnished results consistent with a pH-dependent formation of phosphatidylinositol monophosphate-enriched microdomains. The domain formation was most pronounced between pH approximately 7 and approximately 9.5, whereas slightly acidic pH values (pH 4) resulted in the disintegration of the domains. This pH-dependent phosphatidylcholine/phosphatidylinositol monophosphate demixing was observed for the gel phase (FTIR experiments) as well as for the fluid lipid phase (FRET measurements). The observed microdomains are presumably stabilized by hydroxyl/hydroxyl as well as hydroxyl/phosphomonoester and phosphodiester interactions. While the pH dependence of the mutual phosphatidylinositol monophosphate interaction was largely the same for all investigated phosphatidylinositol monophosphates, it turned out that the relative stability of phosphatidylinositol monophosphate-enriched microdomains (pH 7-9.5) was governed by the position of the phosphomonoester group at the inositol ring (PI-4P > PI-5P > PI-3P). Demixing was also observed for phosphatidylcholine/phosphatidylinositol mixed vesicles; however, in this case the microdomain formation was only slightly affected by pH changes.

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Section: Phosphatidylcholine/phosphatidylinositol Monophosphate Mixed Vesiclessupporting

confidence: 69%

Domain Formation in Phosphatidylinositol Monophosphate/Phosphatidylcholine Mixed Vesicles

Redfern

Gericke

2004

Biophysical Journal

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“…5 in Kooijman et al (18)). Similarly complex ionization behavior was also observed for the corresponding inositol bisphosphates and trisphosphates (see the Supporting Material) (25,26). Although this biphasic behavior of the protonation state of the respective phosphate could be modeled simply with a two-pK a Henderson-Hasselbach relation, this is an inaccurate representation, as each phosphate group actually undergoes only a single deprotonation event in the pH range 4-11, i.e., from À1 to À2 charge.…”

Section: Multistate Fitting Modelmentioning

confidence: 84%

“…To describe this complex ionization, a separate pK a (also referred to as ''micro-pK a '') value is used to describe the deprotonation of a phosphate group when its partner(s) are protonated versus when they are deprotonated, in a similar manner to that described by Schlewer et al (26) for the inositol polyphosphates. For PI(3,4,5)P 3 , with its three phosphomonoester groups, there are eight distinct ionization states in the pH range of 4-11-one fully protonated state (three remaining protons), three singly deprotonated states, three doubly deprotonated states, and one fully deprotonated state.…”

Section: Multistate Fitting Modelmentioning

confidence: 99%

Effect of H-Bond Donor Lipids on Phosphatidylinositol-3,4,5-Trisphosphate Ionization and Clustering

Graber

Thomas

Johnson

et al. 2018

Biophysical Journal

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The phosphoinositide, phosphatidylinositol-3,4,5-trisphosphate (PI(3,4,5)P), is a key signaling lipid in the inner leaflet of the cell plasma membrane, regulating diverse signaling pathways including cell growth and migration. In this study we investigate the impact of the hydrogen-bond donor lipids phosphatidylethanolamine (PE) and phosphatidylinositol (PI) on the charge and phase behavior of PI(3,4,5)P. PE and PI can interact with PI(3,4,5)P through hydrogen-bond formation, leading to altered ionization behavior and charge distribution within the PI(3,4,5)P headgroup. We quantify the altered PI(3,4,5)P ionization behavior using a multistate ionization model to obtain micro-pK values for the ionization of each phosphate group. The presence of PE leads to a decrease in the pK values for the initial deprotonation of PI(3,4,5)P, which describes the removal of the first proton of the three protons remaining at the phosphomonoester groups at pH 4.0. The decrease in these micro-pK values thus leads to a higher charge at low pH. Additionally, the charge distribution changes lead to increased charge on the 3- and 5-phosphates. In the presence of PI, the final deprotonation of PI(3,4,5)P is delayed, leading to a lower charge at high pH. This is due to a combination of hydrogen-bond formation between PI and PI(3,4,5)P, and increased surface charge due to the addition of the negatively charged PI. The interaction between PI and PI(3,4,5)P leads to the formation of PI and PI(3,4,5)P-enriched domains within the membrane. These domains may have a critical impact on PI(3,4,5)P-signaling. We also reevaluate results for all phosphatidylinositol bisphosphates as well as for PI(4,5)P in complex lipid mixtures with the multistate ionization model.

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“…As will be shown later, the third equivalent of added protons mainly binds to an adenine nitrogen, so that K 3 satisfactorily defines the last protonation step. 31 P NMR has proven to be a good probe to study individual protonation, [29][30][31][32][33][34][35][36][37][38][39][40] provided that the observed chemical shifts for the phosphorus resonances δ i obs mainly depend on the electronic effects accompanying the variations in the protonation states. In that case, the protonated fraction f i,p of a phosphate group in position i on compounds 1e or 1a can be calculated by the eq 1:…”

Section: Potentiometric Studies and Nmr Determinationsmentioning

confidence: 99%

“…31 P NMR has proven to be a good probe to study individual protonation, − provided that the observed chemical shifts for the phosphorus resonances mainly depend on the electronic effects accompanying the variations in the protonation states. In that case, the protonated fraction f i ,p of a phosphate group in position i on compounds 1e or 1a can be calculated by the eq 1: where δ i, p and δ i ,d correspond, respectively, to the chemical shifts of the protonated and deprotonated fractions of the phosphates in position i .…”

Section: Potentiometric Studies and Nmr Determinationsmentioning

confidence: 99%

Novel Antagonists Acting at the P2Y₁ Purinergic Receptor: Synthesis and Conformational Analysis Using Potentiometric and Nuclear Magnetic Resonance Titration Techniques

et al. 2002

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The human P2Y(1) receptor is widely distributed in many tissues and has a classical structure of a G protein-coupled receptor. Activated by adenosine-5'-diphosphate (ADP), this receptor is essential for platelet aggregation. In the present paper, we describe the synthesis of novel P2Y(1) antagonists that could be of interest at least as tools to define the physiological roles of the P2Y(1) receptor, at best as new antithrombotic agents. Thus, we prepared the 2,N(6)-dimethyl-2'-deoxyadenosine-3',5'-bisphosphate derivative, 1e. The biological activity was demonstrated by the ability of compound 1e to inhibit ADP-induced platelet aggregation, shape change, and intracellular calcium rise. This compound was a full antagonist at the P2Y(1) receptor with a pA(2) value of 7.11 +/- 0.11 and was found to be 4-fold more potent than the reference N(6)-methyl-2'-deoxyadenosine-3',5'-bisphosphate (1a, pA(2) = 6.55 +/- 0.05), revealing the potency-enhancing effects of the 2-methyl group. The better activity of 1e as compared to 1a was analyzed using both potentiometric and nuclear magnetic resonance titration techniques, which highlighted specific conformational features of this compound. These results clearly indicate the preference for both compounds for an anti conformation at the N-glycosyl linkage. Furthermore, the percentage of S conformer of 1e is close to that of 1a, which is nearly 70% at pH = 2.8 and increases dramatically when pH increases. From the macroprotonation constants, it can be noted that compound 1e is significantly more basic than 1a. This is indeed expected for the N1 adenine nitrogen due to the electron-donating character of the methyl moiety. By considering the microconstants of the phosphate groups, the higher basicity of P3 and P5 for 1e may be due to the decrease in the local dielectric constant induced by the substitution of the hydrogen atom by a more lipophilic methyl group. Thus, it may be suggested that the gain in activity of 1e when compared to the reference compound 1a would result from its gain in basicity rather than steric and conformational modifications. The synthesis of the first selective radioligand acting at the P2Y(1) receptor ([(33)P]-N(6)-methyl-2'-deoxyadenosine-3',5'-bisphosphate, 17) is also reported and will be used in the future for efficient screening needed for drug optimization.

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Inositol Phosphates: Inframolecular Physico-Chemical Studies: Correlation with Binding Properties

Cited by 5 publications

References 0 publications

Domain Formation in Phosphatidylinositol Monophosphate/Phosphatidylcholine Mixed Vesicles

Domain Formation in Phosphatidylinositol Monophosphate/Phosphatidylcholine Mixed Vesicles

Effect of H-Bond Donor Lipids on Phosphatidylinositol-3,4,5-Trisphosphate Ionization and Clustering

Novel Antagonists Acting at the P2Y₁ Purinergic Receptor: Synthesis and Conformational Analysis Using Potentiometric and Nuclear Magnetic Resonance Titration Techniques

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Inositol Phosphates: Inframolecular Physico-Chemical Studies: Correlation with Binding Properties

Cited by 5 publications

References 0 publications

Domain Formation in Phosphatidylinositol Monophosphate/Phosphatidylcholine Mixed Vesicles

Domain Formation in Phosphatidylinositol Monophosphate/Phosphatidylcholine Mixed Vesicles

Effect of H-Bond Donor Lipids on Phosphatidylinositol-3,4,5-Trisphosphate Ionization and Clustering

Novel Antagonists Acting at the P2Y1 Purinergic Receptor: Synthesis and Conformational Analysis Using Potentiometric and Nuclear Magnetic Resonance Titration Techniques

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Product

Resources

About

Novel Antagonists Acting at the P2Y₁ Purinergic Receptor: Synthesis and Conformational Analysis Using Potentiometric and Nuclear Magnetic Resonance Titration Techniques